Ocular Fixation And Stabilization Device For Ophthalmic Surgical Applications

ABSTRACT

An interface for coupling an eye to a surgical laser is disclosed. A lens cone includes a base ring opposite an apex ring. The base ring defines a first plane and is adapted to couple to the delivery tip of the laser such that the first plane has a predetermined position relative to the delivery tip. An applanation lens is affixed to the apex ring and has a surface disposed in a second plane such that the second plane is parallel to and has a predetermined position relative to the first plane. A gripper is engagable with the lens cone. An attachment ring is affixed to the gripper and is adapted to couple to the anterior surface of the eye. When the lens cone and gripper are engaged, the applanation lens contacts the anterior surface of the eye, placing the anterior surface in spatial registration with the delivery tip.

BACKGROUND OF THE INVENTION

1. Priority

Priority is claimed as a continuation application to U.S. patentapplication Ser. No. 10/865,165, filed Jun. 10, 2004, now U.S. Pat. No.7,018,376, which is a divisional application of U.S. patent applicationSer. No. 09/772,539, filed Jan. 29, 2001, now U.S. Pat. No. 6,863,667.The disclosures of each of the aforementioned priority documents areincorporated herein by reference in their entirety.

The present application is related to U.S. Pat. No. 6,254,595 and U.S.Pat. No. 6,344,040, the disclosures of which are incorporated herein byreference.

2. Field of the Invention

The present invention relates to an interface device for ophthalmiclaser surgery and, more particularly, an interface apparatus used tostabilize the eye of a patient with respect to a laser beam duringophthalmic surgery, and to reconfigure the cornea for precision laserinteraction.

3. Background

In recent years, significant developments in laser technology have ledto its application in the field of ophthalmic surgery. In particular,laser surgery has become the technique of choice for ophthalmic surgicalapplications. In certain ophthalmic laser procedures, surgeons use amechanical device termed a microkeratome to cut a layer of the anteriorsurface of the cornea in order to expose the underlying corneal stromato which the laser is applied. However, complications surrounding theuse of the microkeratome and its metal blade have resulted in researchinto improved techniques that are performed exclusively by a lasersystem. Such all-laser techniques obviate the need for mechanicaldevices pre- or post-operatively, and provide significantly improvedprecision.

Despite these advances in laser technology, the use of such systems forophthalmic surgical procedures remains fraught with substantialmechanical limitations, particularly in the area of developing a stableinterface between an incident laser beam and the eye of a patient.Ophthalmic surgery is a precision operation and requires a very precisecoupling between the surgical tool (i.e., the laser beam) and the regionto be disturbed (i.e., a portion of the patient's eye). Even a verysmall movement of the eye with respect to the intended focal point ofthe laser beam can not only lead to non-optimal results, but might evenresult in permanent damage to non-renewable tissue within the eye,leading to precisely the opposite result than that desired. Given thateye movement is often the result of autonomic reflex, it should beunderstood that there must be some means of stabilizing the position ofa patient's eye with respect to an incident laser beam in order to avoidthe intolerable consequence of relative movement.

Heretofore, the major technique used to compensate for relative eyemotion with respect to an incident laser beam, has been to have thepatient focus on a stationary target. This involves providing a visualtarget to the eye undergoing surgery, and requiring that the patientretain focused on the perceived target feature. While this technique hasprovided some small benefit, it places all of the burden of minimizingrelative motion upon the patient, and does not allow for any grossautonomic reflex motions, e.g., as when the patient might be startled.In this technique, the target provides optical interface, while thepatient's conscious responses provide the feedback mechanism.

An additional technique involves the use of an optical eye trackingapparatus, whereby a selected eye feature is targeted for monitoring byan optical device, and as the targeted feature displaces as the resultof eye movement, its displacement is characterized and fed into theincident laser beam control apparatus as a compensation signal. Thissecond technique offers a substantial improvement over the first,particularly when it is implemented in addition to a patient-driventarget focusing mechanism. However, such systems are inordinatelyexpensive since a second, completely independent optical path must beprovided between a patient's eye and a surgical apparatus in order toaccommodate the eye tracking apparatus. Further expense and complexityis incurred when it is considered that an eye tracking apparatusrequires an additional software component in order to be operative,which software component must be integrated into a laser deliverysystem. Considerations of interoperability must be met as well as theprovision for an automatic shutdown of the laser system in the event ofthe loss of target feature lock.

Accordingly, a simple mechanical system, if properly designed, is ableto best meet the imperatives of interfacing a laser delivery system witha target object. If the goal is to minimize relative analog motion, ananalog stabilization device would necessarily offer the mostadvantageous solution. In this regard, certain mechanical stabilizationdevices have been proposed, particularly, a corneal applanation devicewhich is the subject of U.S. patent application Ser. No. 09/172,819,filed Oct. 15, 1998 and commonly owned by the assignee of the presentinvention, the entire contents of which are expressly incorporatedherein by reference. Such a mechanical device directly couples apatient's eye to the laser's delivery system being affixed to both thelaser and the anterior surface of a patient's cornea. The cornealcoupling, in these devices, is typically implemented by lowering anapplanation fixture over the anterior surface of the cornea underpressure. It is assumed in these forms of devices that pressure appliednormal to the corneal surface will restrict conventional motion of thecornea thereby stabilizing the eye along a major access normal to thedevice.

However, although this assumption may hold true in a large number ofcases, it certainly interface should be established with the iriscentered, for best results. The actual establishment of an effectivedevice/corneal interface is an exercise in trial-and-error, resulting ina great deal of frustration to doctor and patient, as well asconsiderable eye fatigue.

For ophthalmic laser procedures where eye tissue is to bephotodisrupted, it is extremely important for the laser beam to beproperly focused to a specific focal spot in the tissue that is to beeffected. Not only is it extremely important to have good focaldefinition, but also that the focal point have the proper dimensionality(i.e., the correct spot diameter and shape). In order to accommodatethis, it is necessary for the laser beam to be as free from aberrationsas possible. In particular, for ophthalmic laser procedures involvingthe cornea, it happens that the spherical geometry of the corneaintroduces optical aberrations as a result of its shape, which areseparate and distinct from aberrations introduced by the laser's ownoptical system. Significantly, these corneal induced aberrations distortthe definition of the focal spot of a laser beam as the beam is focusedto a position within corneal tissue.

Due to the spherical geometry of the anterior surface of the cornea, twospecific types of aberrations are of particular importance with regardto beam distortion; spherical aberration (which relates to points on theoptical axis of the laser beam) and coma which relates to points thatare off-axis). Spherical aberration and coma are similar to one anotherin that they both arise from a failure to image or focus optical raytraces onto the same point. Spherical aberration relates to a distortionthat can be characterized as radial in nature, with some radialdirections being stretched while other radial directions are shrunk,converting thereby, an ideally circular spot into an elliptical spot.Coma distortion, on the other hand, implies an elongation along oneradius a circle, resulting in a “comet-like” shape. Accordingly, anystructure which interfaces between a curved, anterior surface of thecornea and laser delivery system must be applanatic in nature. Bydefinition, an applanatic lens is one which is free from both sphericalaberration and coma.

As is recognized by the present invention, applanatic refraction at theanterior surface of the cornea can be effectively accomplished byflattening the anterior surface. With such a corneal reconfiguration,the beam will be free of aberrations (other than chromatic) which wouldotherwise result from an interface with the cornea's native sphericalanterior surface.

In view of the foregoing, it is thus evident that there is a need for asimple mechanical interface device that is able to stabilize the eyeagainst relative motion with respect to a laser beam used for ophthalmicsurgical procedures without relying on secondary mechanicalconsiderations, such as surface tension, friction, or the like. Such adevice should be able to present an optical feature to an incident laserbeam in a stable, well characterized location, such that the beam isable to interact with the feature without regard to opto/electronicfeedback mechanisms. In addition to maintaining a proper orientationbetween the eye and a laser delivery system during ophthalmic lasersurgery, such a device should applanate the eye during surgery whilereducing inter-ocular pressure during the surgical procedure. Such adevice should be easy for a clinician to affix, as well as being simpleand cost effective to manufacture and use.

SUMMARY OF THE INVENTION

The present invention is directed toward an interface for coupling apatient's eye to a surgical laser and a method for the same. A lens coneincludes a base ring and an apex ring. The base ring defines a firstplane and is adapted to couple to a delivery tip of the surgical lasersuch that the first plane is at a predetermined position relative to thedelivery tip. An applanation lens is affixed to the apex ring. Theapplanation lens has a surface disposed in a second plane such that thesecond plane is parallel to and at a predetermined position relative tothe first plane. A gripper is adapted to engage the lens cone. Anattachment ring is affixed to the gripper and is adapted to couple tothe anterior surface of the eye.

In a first separate aspect of the present invention, coupling theattachment ring to the eye results in the applanation lens contactingthe anterior surface of the eye. This places the anterior surface of theeye in spatial registration with the delivery tip of the surgical laser.

In a second separate aspect of the present invention, the applanationlens includes an applanation surface which is placed into contact withthe anterior surface of the eye. This applanation surface preferablydefines the second plane and deforms to the anterior surface of the eye.

In a third separate aspect of the present invention, the grippercomprises a pair of expandable jaws disposed adjacent a central orifice.These jaws are adapted to engage the apex ring of the lens cone.Preferably, the gripper further comprises opposing lever handles coupledto the jaws. These opposing lever handles may be adapted to expand thejaws to facilitate coupling between the gripper and the lens cone.

In a fourth separate aspect of the present invention, the applanationlens includes an applanation surface which is placed into contact withthe anterior surface of the eye. This applanation surface preferablydefines the second plane and deforms to the anterior surface of the eye.

In a fifth separate aspect of the present invention, any of theforegoing aspects may be employed in combination.

BRIEF DESCRIPTION OF THE DRAWINGS

These and other features, aspects and advantages of the presentinvention will be more fully understood when considered in connectionwith the following specification, appended claims and accompanyingdrawings wherein:

FIG. 1, is an exploded, perspective illustration of the componentportions of an ocular stabilization and applanation device in accordancewith the present invention;

FIG. 2, is a simplified, top plan view of the gripper/interfacestructure suitable for use in connection with the ocular stabilizationand applanation device of FIG. 1;

FIG. 3, is a simplified, side view of the gripper/interface structuresuitable for use in connection with the ocular stabilization andapplanation device of FIG. 1;

FIG. 4, is a perspective illustration of a lens cone, interfacing with agripper/interface structure, and incorporating an applanation lens inaccordance with the invention;

FIG. 5, is a simplified, cross-sectional illustration of an attachmentring, suitable for use in connection with the ocular stabilization andapplanation device of FIG. 1;

FIG. 6, is a simplified, cross-sectional illustration of the attachmentring of FIG. 5, illustrating the coupling of the attachment ring to theanterior surface of a patient's eye, and indicating applanation of thecorneal surface;

FIG. 7, is a simplified, cross-sectional illustration of a firstembodiment of an applanation lens disposed within an attachment ring;

FIG. 8, is a simplified cross-sectional illustration of the ocularstabilization and applanation device of FIG. 1, showing operation of thedevice to applanate the corneal surface of an eye.

FIG. 9, is a simplified, cross-sectional illustration of a secondembodiment of an applanation lens disposed within an attachment ring;and

FIG. 10, is a simplified, semi-schematic illustration of the top surfaceof a gripper/interface device and showing radial alignment guides, inaccordance with the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Conceptually, the present invention is directed to a mechanicalapparatus that performs the functions of coupling the anterior surfaceof a target eye to a surgical laser and applanating said eye. Theapparatus is termed mechanical because it directly couples themechanical surface of an operative target, such as human corneal tissue,to a mechanical fixture of a surgical laser system, such as the distaltip of a laser beam's delivery system. Simply put, and in the context ofa particular embodiment which will be described in greater detail below,the apparatus is affixed to the anterior surface of a human cornea andis affixed to the laser delivery system.

Referring initially to the exemplary embodiment of FIG. 1, anillustrative ocular fixation and applanation device is shown in anexploded, perspective view, and is generally indicated at 10. The ocularfixation and applanation device (referred to herein as simply anapplanation device or alternatively, a patient interface) is anapparatus that attaches to a human eye and holds (fixes) the eye in allthree axes (x, y and z) from translational and rotational movement withrespect to the incident beam of a laser surgical device. In addition,the applanation device allows for the cornea of the eye to be applanatedby a lens (laser optic) for efficient ophthalmic surgery. Once the eyeis applanated by an external force, the applanation device grips, holdsor affixes the eye to the applanation lens, or laser optic, during alaser surgical procedure, so as to minimize or preclude differentialmotion of the human eye with respect to the laser optical path duringthe laser procedure.

With regard to the exemplary embodiment of FIG. 1, the applanationdevice 10 is comprised of a number of component parts that may bedisposable (i.e., used once and discarded) and/or re-usable. In thisregard, the applanation device 10 suitably comprises an ocularattachment ring 12, by means of which the applanation device 10 iscoupled to the eye, a gripper fixture 14, a lens cone fixture 16 and anapplanation lens 18, which in combination with the lens cone 16 is usedto applanate a patient's cornea and establish an appropriate opticalpath alignment between the cornea and a laser optical path.

The component parts of the applanation device 10 are illustrated inexploded view, and are intended to be collapsed vertically, such thateach of the individual portions of the device are in mechanicalengagement with appropriate other portions, such that the completeddevice is provided in a generally unitary structure. This is not to saythat the devices' component parts are permanently affixed to oneanother: indeed, the component parts are separable and interchangeableat will. Rather, the applanation device 10 is intended to form a singlecomposite interface structure between a human cornea and a surgicallaser once the component parts have been aligned with a patient's eyeand with respect to the laser delivery system, as will be described indetail below.

As illustrated in the exemplary embodiment of FIG. 1, the attachmentring 12 forms the mechanical interface between the anterior surface of ahuman cornea and the remaining structure of the applanation device. Theattachment ring 12 is constructed of a flexible, hypoallergenic materialsuch as rubber, hypoallergenic plastic, silicone, or the like. Theattachment ring 12 is substantially annular in shape, having a generallysmooth exterior surface and a highly articulated and functional innersurface, as will be described in greater detail below. Being annular inshape, the attachment ring 12 necessarily defines an outer diameter (OD)and inner diameter (ID), with the inner diameter circumscribing acentral target opening 13. The absolute value of its outer diameter isnot particularly relevant to practice the principles of the presentinvention, but the value of the inner diameter is suitably chosen suchthat when the attachment ring 12 is placed over a patient's eye, theattachment ring's central opening, defined by the inner diameter,completely circumscribes a sufficient area of corneal tissue such that asurgical laser procedure may be completely performed within the exposedarea without having to displace the attachment ring.

The attachment ring 12 is disposed and retained within an appropriatelyshaped female-type receptacle provided in the underside of thegripper/interface structure 14. Since the attachment ring 12 isconstructed of a flexible material, the female receptacle of the gripperstructure 14 need only have an ID of a dimension slightly smaller thanthe OD of the attachment ring, such that the attachment ring may fitwithin the receptacle and be held in place by compressive force.

The gripper/interface structure 14 of the exemplary embodiment of FIG. 1is detailed in the top plan view illustration of FIG. 2 and the sideview illustration of FIG. 3. In general, the gripper/interface 14functions much like a clothes pin, and is constructed with a gripperportion 19, overlaying a receiver portion 20 that is designed to receiveand contain the attachment ring 12 within a central opening 21 thatpasses through both the gripper portion and the receiver portion. Thegripper portion 19 is constructed as a lever, characterized by two leverhandles 22 and 24 separated by a closure spacing 25. As the leverhandles are squeezed together, the closure spacing 25 closes and adeformation force is transmitted to two jaws 26 and 27 surrounding thecentral opening 21. Applying a deformation force causes the jaws 26 and27 to further separate, in turn causing the central opening to increasein area. Pinching the lever handles 22 and 24 together forces the jaws26 and 27 to widen sufficiently for a cylindrical object to be insertedinto the now-widened central opening 21. Once the pressure on the leverhandles is relaxed and the jaws close to their nominal position, theinside surfaces of the jaws 26 and 27 compress against the object andretain the object in position in the central opening 21. This particularfeature is pertinent to the present invention when it is considered thatthe gripper/interface device 14 must couple the attachment ring 12 tothe lens cone fixture 16 in a relatively secure manner and with acharacterizable geometric relationship.

The receiver portion 20 is disposed below the jaws of the gripperportion and lays in a plane parallel to that of the gripper portion. Thereceiver portion is cantilevered forward from the space between thelever handles and the jaws and is separated from the gripperjaws by aslight spacing. The receiver portion is substantially annular in shapewith the central opening 21 extending therethrough. Thus, it will benoted that when the gripper portion jaws 26 and 27 are opened, only thecentral opening portion defined in the gripper portion 19 is widened.The central opening portion extending through the receiver portion 20maintains its diameter.

This particular feature allows the attachment ring 12 to be maintainedwithin the central opening portion of the receiving portion, when thegripper jaws are opened. Likewise, the gripper jaws may be opened toreceive, for example, the lens cone, without disturbing or displacingthe attachment ring.

In this regard, and in connection with the perspective illustration ofFIG. 4, the lens cone fixture 16 is suitably constructed as anopen-sided truncated cone-like structure, with an open, annular basering 28 affixed to an open, cylindrical apex ring 30 by a set of supportstruts 32 which extend between the base ring 28 and the apex ring 30.The base ring 28 is larger than the apex ring 30 thereby giving the lenscone 16 its characteristic truncated cone-like shape.

Being cylindrical in construction, the apex ring 30 will be understoodto comprise an inner diameter (ID) and an outer diameter (OD), whereinthe OD is dimensioned such that it is only slightly larger than the IDof the central opening portion 21 of the gripper portion 19 of thegripper/interface structure 14. The lens cone structure 16 isconstructed of a substantially rigid material such as a rigid, extrudedplastic, aluminum, or the like, such that the OD of the apex ring 30would not be expected to substantially deform under pressure,particularly not under the compression forces applied by the jaws of thegripper.

Accordingly, the lens cone fixture 16 would not precisely fit into theID of the central opening 21 of the gripper/interface structure 14 undernormal circumstances. However, once compressive force is applied to thelever handles 22 and 24, that force is applied to the remainder of thestructure, causing the jaws 26 and 27 to open and the interior diameterof central opening 21 to increase in consequence. The OD of the apexring 30 of the lens cone structure 16 is able to then be inserted intothe central opening 21 of the gripper/interface structure 14 and, whenpressure is released on the lever handles 22 and 24, the jaws 26 and 27close upon the apex ring 30 thereby grasping the apex ring andestablishing a fixed relationship between the lens cone 16 and thegripper/interface structure 14. Since the gripper/interface structure 14is in geometric engagement with the attachment ring 12, and since theattachment ring 12 is coupled to corneal tissue, it should be understoodthat the lens cone fixture 16 is now held in a particular spatialrelationship (alignment) with the surface of the cornea.

As will be described in greater detail below, the apex ring 30 defines areceptacle for receiving and retaining an applanation lens 18. It is theintention of the invention to place the applanation lens 18 in proximatecontact with a human cornea, and since it is the function of theattachment ring 12 to mechanically interface with a human eye, it shouldbe understood that the gripper/interface structure 14 functions toprovide an alignment and coupling interface between the lens conefixture, including the applanation lens 18, and the attachment ring 12,and thereby the patient's eye. With regard to the laser delivery system,it will be understood that the base ring portion 28 of the lens conefixture 16 is adapted to be affixed to the distal end of a laser opticaldelivery system, such that the delivery system need only be concernedwith focusing an incident laser beam at a particular point in space. Aswill be further described below, the surface of the applanation lens incontact with corneal tissue (the applanation surface) is disposed at aspecific distance from the interface between the base ring and the laserdelivery system, such that the anterior corneal surface, or at leastthat portion in contact with the applanation lens, is at a knownspecific distance from the laser delivery tip. The surface of the corneanow resides along a plane at a distance known to the laser.

An exemplary embodiment of an attachment ring, generally indicated at12, is illustrated in the exemplary, cross-sectional diagrams of FIGS. 5and 6, where FIG. 5 illustrates the attachment ring alone, and FIG. 6illustrates the attachment ring as it would be applied to the anteriorsurface of a patient's eye. Recall that it is the function of theattachment ring 12 to provide a primary interface with an operativetarget, such as a human eye, and a laser delivery system. In thisregard, the operative target is represented as the corneal portion 34 aof a human eye 34 in the exemplary embodiment of FIG. 6, and to whichthe attachment ring 12 is illustrated as being affixed. In the exemplaryembodiment of FIG. 5, the attachment ring 12 is illustrated as having aninterior and exterior portion, the exterior portion of which ischaracterized by a lower skirt 36 which functions as a shroud that comesinto intimate contact with the anterior portion of the human eye 34. Theshroud 36 has a relatively thin cross-section and is deformable so as toestablish and maintain conformal contact with the anterior cornealsurface. The shroud or skirt portion 36 extends upwardly into a crownsurface 38 which maintains a substantially uniform ID againstdeformations of the lower shroud portion 36 in response to pressureagainst the shroud portion by the human eye.

The attachment ring 12 further includes an interior, annular ring member40 which is disposed on and protrudes outwardly from the interiorsurface of the attachment ring. The annular ring member 40 protrudesoutwardly in a direction normal to the interior surface of theattachment ring, on its top surface, but is formed with a bottom surfacethat includes an upwardly extending cavity 42, with the cavity formedbetween a bottom portion of the annular ring member 40 and a proximateportion of the interior surface of the attachment ring 12. Thus, itshould be understood that the cavity 42 formed by the shape of theannular ring member 40 defines an annular cavity, with its openingpointing towards the bottom, shroud or skirt portion of the attachmentring.

In the particular exemplary embodiment of FIGS. 5 and 6, the attachmentring 12 further includes an attachment fitting 44 which extends, in aradial direction, from the exterior surface of the attachment ring. Theattachment fitting 44 includes a central orifice 46, disposed along itsentire length, and which passes through the material of the attachmentring's skirt portion 36, such that a communication path is openedbetween the annular channel 42, at one end, and the distal end of theattachment fitting 44. The attachment fitting 44 might be constructed ofthe same material as the attachment ring, indeed the entire apparatusmight be formed or molded as single piece. Alternatively, the attachmentfitting 44 might be a separate small piece of plastic, metal, or someother material that is coupled to the attachment ring 12 at any stage inthe manufacturing or assembly process of the applanation device 10. Itshould also be noted that if the attachment fitting 44 were to beconstructed from the same pliant, flexible rubber, silicone or plasticmaterial as the attachment ring, a suitable female receptacle can beprovided on the underside of the gripper structure 14 in proximity toand extending from the central opening 21 thereof. As the attachmentring 12 is friction-fit into place within the gripper 14, the attachmentfixture 44 is also press-fit into its corresponding female receptacle,thereby orienting and retaining the entire attachment ring structurewithin the gripper 14, by compressive force.

Additionally, and as best seen with respect to FIG. 1, the attachmentfixture 44 might be accessed by inserting one side of a male-to-malefitting coupler 45 (FIG. 1) into the central orifice 46 and coupling theother side to a length of small diameter, medical grade tubing. Thetubing is then coupled to a vacuum source which, in turn, is then ableto apply a vacuum to the annular channel 42 through the attachmentfixture 44. Alternatively, attachment ring 12 may be configured withprojections, such as “teeth”, “bumps”, or some such other gripping orfriction inducing structure, that would serve to attach the attachmentring to the eye without the need for suction.

In operation, and with regard to the particular exemplary embodiment ofFIG. 6, the ocular attachment ring 12 is placed around the limbus of apatient's eye 34, such that its lower, skirt portion 36 surrounds theanterior surface of the cornea 34 a, thereby leaving free optical accessto the cornea 34 a. A slight compressive force is applied to theattachment ring, thereby deforming the skirt portion 36 in an outwardlydirection, such that it tends to conform to the shape of the cornealsurface. A slight vacuum is developed by a vacuum source or suction pumpand coupled to the attachment ring through the attachment fitting 44. Assuction is applied to the attachment fitting 44, its internal orifice 46couples the suction to the annular channel 42 which is now sealed-offfrom the external ambient environment by corneal contact with the skirtportion 36 (forming one side of the channel) and a contact edge 50 ofthe annular ring member 40 (forming the other surface of the channel). Avacuum is thereby developed within the annular channel 42 which, inturn, couples the attachment ring 12 to the corneal surface 34 a,thereby fixing the eye to the attachment ring which, when it is itselfcoupled to the rest of the structure, as will be described in greaterdetail below, fixes the eye against relative movement.

It should be noted, in connection with the embodiment of FIG. 6, that inits preferred form, the attachment ring 12 is affixed to the gripperstructure 14, prior to the attachment ring's being coupled to an eye.The gripper is not shown as being already attached to the attachmentring in order that the particular structural and functional details ofthe attachment ring may be shown simply and without regard to additionaland potentially confusing structure. Further, and as will be describedin greater detail below, two corneal surface shapes are depicted in theillustrated embodiment of FIG. 6, a rounded surface 34 a, indicating thenormal shape of the cornea, and a flattened surface 34 b indicating theeffects of applanating the corneal surface. Applanation is discussedfurther in this specification, but it is worth noting that as thegripper/ring structure is affixed to the eye 34, the structure surroundsthe limbus, leaving the corneal area open to access. The corneal surfaceremains substantially rounded, at this point, and is only contoured orflattened after introduction of the applanation cone 16 into the gripperand contact is made between the applanation lens 18 and the cornea 34 a.The applanated corneal surface 34 b then takes on a shape imposed by theshape of the contact surface (applanation surface) of the applanationlens.

In the particular exemplary embodiment of FIG. 6, the vacuum or suctiondeveloped by the vacuum source or suction pump is transmitted to theattachment fitting 44 by small-bore tubing. The suction might be appliedby coupling the tip of a syringe to the attachment fitting 44 and byintroducing a vacuum in the body of the syringe. That vacuum istransmitted to the attachment ring by a small-bore tubing, a bluntcanula, or the like. All that is required is that a vacuum (partial orotherwise) be formed within the annular channel 42 such that it is ableto provide a coupling force between the attachment ring and the cornealsurface.

Turning now to FIG. 7, it will be appreciated that the lens cone 16affords similar functionality to the attachment ring 12, in that thelens cone 16 provides the primary interface and attachment between theapplanation device (10 of FIG. 1) and the delivery tip of a surgicallaser system. In this regard, the base ring 28 is rigidly coupled to thelaser delivery system. Attachment between the two structures may be madein a number of ways, while remaining within the scope of the invention.In particular, the base ring 28 may be provided with slot-shaped cutoutswhich are mated with retaining pins provided on the delivery system,with the base ring being inserted over the pins and rotated in order tocreate an interlock. Alternatively, the base ring can be screwed intoplace on the delivery tip or, the delivery tip might be provided withrotatable “dogs” which are rotated into place over the base ring 28thereby securing the base ring into position. The means by which thebase ring and thus the lens cone 16 are affixed to the delivery tip isnot particularly material to practice the principals of the invention.All that is required is that the lens cone 16 be affixed to the deliverytip such that it is incapable of independent relative movement withrespect to the delivery tip. In this regard, it should be noted that thebase ring has a top surface defining a generally horizontal plane (an x,y plane). The delivery tip is provided with a similar planar surfacewhich is mated with the planar base ring surface. An x, y plane definingone aspect of ocular applanation is thereby established.

As illustrated in the exemplary, cross-sectional diagram of FIG. 7, thelens cone's apex ring 30 extends downwardly away from the base ring 28and is held in a particular spatial relationship by struts 32, extendingbetween the apex ring 30 and the base ring 28. The base ring 30 is asubstantially cylindrical structure with outer and inner wall surfacesand with a wall thickness sufficient to support reasonable rigidityunder compressive stress. An applanation lens 18 is disposed within theapex ring 30 and has an OD substantially the same as the ID of the apexring such that it fits into the apex ring and rests against the ring'sinterior wall surface. The applanation lens 18 is then bonded into placeforming a generally unitary structure with the lens cone 16. Theapplanation lens 18 is formed with an anterior surface 64 and anapplanation surface 66. It is to be appreciated that both the anteriorsurface 64 and the applanation surface 66 are substantially flat andsubstantially parallel to one another. The applanation lens 18 issuitably constructed from a quartz silicate glass or an optical qualityplastic chosen for its transmission characteristics of light at theparticular wavelength delivered by the laser system under consideration.

Manufacture of the lens cone involves bonding and alignment of theapplanation lens 18 to the apex ring 30. Both of these operations(bonding and alignment) are performed at substantially the same time.The lens cone 16 is placed in registration with an alignment and bondingfixture, termed a “golden pedestal”. The golden pedestal has ahorizontal alignment plane (an x, y plane) which is positioned parallelto the x, y plane defining the base ring 28. An applanation lens 18 ispositioned on the golden pedestal such that its parallel anterior andapplanation surfaces lie in the x, y plane defined by the pedestal and,thus the base ring. The lens cone is lowered over the lens until thelens is positioned within the apex ring portion, all the whilemaintaining the relationship between the various x, y planes. When thelens is in position, it is bonded, with a suitable glue, such as a UVcuring cement, to the inside surface of the apex ring, thereby fixingthe applanation lens in a specific plane, with respect to the base ring,and at a specific distance from the base ring. Accordingly, it will beappreciated that the applanation lens is established in a specific x, yplane and at a specific z distance from the base ring, itselfestablished in a specific x, y plane and at a specific z distance fromthe delivery tip of a surgical laser. A known spatial relationshipbetween the laser and the applanation surface of the applanation lens isthereby defined.

It is an important feature of the present invention that the lower,contact, or applanation, surface of the applanation lens is disposed inspace in a particular relationship with the laser delivery tip. Thecontact surface provides a reference surface from which the laser systemis able to compute a depth of focus characteristic. Since the positionof the contact surface is known, with respect to the delivery tip, sotoo is the position of the applanated corneal surface. It is, therefore,a relatively straightforward matter to focus a laser beam to any pointwithin the cornea. One needs only to calculate the focal point withrespect to the contact surface of the lens, in order that the same focalpoint be obtained within the eye.

Aligning the lens into position with respect to the lens cone structureby use of a “golden pedestal” allows alignment tolerances which aresubstantially tighter than those currently obtainable by conventionalmicrokeratome techniques. Conventional microkeratomes typically exhibitoff-plane errors in the range of about +/−30 to +/−40 microns. Thisalignment error leads to planar tilt in the corneal flap, and topotentially dangerous flap thickness variations. For example, if a flapwere created with a 30 to 40 micron error, in the positive thicknessdirection, there exists the possibility that the remaining corneal bedwould not be sufficiently thick to safely conduct a laser ablationprocedure. Instead the cornea would tend to bulge outward, in response,leading to a less than optimum surface shape being presented forsubsequent laser surface ablation. Indeed, it is the very scale ofmicrokeratome depth uncertainty that contributes to the significantpercentage of conventional laser surgery failures.

In accordance with the invention, the “golden pedestal” registration andalignment system allows for planar (in both the x, y plane and the zdirection) alignment tolerances no greater than that of a conventionalmicrokeratome, i.e., in the range of about +/−30 microns, and preferablyin the range of about +/−10 microns. This is measured with respect toboth the planar “tilt” and the z position of the applanation surface ofthe applanation lens with respect to the defined plane of the base ringand, therefore, with respect to the laser's delivery tip. This isparticularly advantageous when it is considered that the applanationsurface is devised to be co-planar with the anterior surface of thecornea, thereby defining a corneal surface which is mathematicallycalculable and precise with respect to the laser delivery tip: the x,yplane of the corneal surface is known and the z distance from the tip tothe surface is also known. Thus, a precise cut may be made within thecorneal material without concern for potentially dangerous depthvariation.

Turning now to FIG. 8, an exemplary embodiment of the complete ocularfixation device 10, as it would be attached to a human eye, isillustrated in cross-sectional form. The lens cone 16 is coupled to theattachment ring 12, thereby coupling a patient's eye 34 to the laserdelivery system, by interfacing the two structures together by thegripper/interface 14. As previously mentioned, the apex ring 30 has anOD sized just slightly larger than the ID of the gripper's annularmating portion 20, such that the apex ring 30 can be inserted into thecentral opening 21 of the gripper 14, when the jaws of the gripper areopened. The apex ring is inserted into the central opening, pressurereleased on the gripping structures 22 and 24 thereby allowing the jawsto relax and to close around and grip the apex ring 30 securely withinthe gripper's central opening. As illustrated in the exemplaryembodiment of FIG. 8, as the apex ring 30 is inserted into the centralopening of the gripper, the applanation surface of the applanation lensmakes contact with a presented portion of the anterior surface of thecornea 34 b. As the lens cone is lowered into proximity with the cornea,the applanation surface of the lens makes contact with the cornea andapplies a pressure to the cornea such that when the lens cone is fullylowered into position, the corneal anterior surface 34 b and theapplanation surface 66 of the lens are in intimate contact with oneanother over a substantial portion of the applanation surface.

Mechanical pressure of the lens causes the corneal surface to conform tothe shape of the applanation surface of the lens. Although depicted inthe exemplary embodiment of FIG. 8 as being flat, the cornea may beformed as a concave or convex surface, depending only on the shape ofthe contact surface of the applanation lens.

In summary, the attachment ring 12 is placed around the limbus of theeye, i.e., centered about the cornea and the pupillary aperture. Thegripper 14 has been previously affixed to the attachment ring 12, suchthat positioning the ring with respect to the eye also positions the eyewith respect to the gripper's central opening, with the pupillaryaperture generally centered within the gripper's opening. Suction isthen applied to the ring in order to attach the ring onto the eye. Withthe eye so presented and held in place by the attachment ring 12, itbecomes a relatively simple matter to lower the lens cone andapplanation lens into proximate contact with the cornea, and retain thelens cone, and particularly the applanation lens, in position by fixingthe apex ring with the gripper. The gripper is opened to receive thecone assembly which is then lowered into the attachment ring.Simultaneously, the contact surface (applanation surface) of the lenscontacts the corneal surface thereby applanating the cornea. The gripperis then closed, thereby clamping the cone assembly in position andfixing the lens relative to the applanated cornea. The eye is held tothe gripper by the attachment ring, while the applanation lens is heldto the eye by the gripper.

As should be understood from the foregoing, and with respect to theexemplary embodiments, the applanation device is substantially rigidlycoupled to the laser delivery system, thus the plane of the applanationsurface 66 is characterizable in space with respect to any given focalpoint of an incident laser beam. With regard to the eye, it should beunderstood that the applanation lens 18 is able to “float” in the “z”direction due to the flexibility of the skirt portion of the attachmentring. The applanation lens 18 is therefore able to accommodate variouslyshaped corneal surfaces without placing undue pressure on the eye.Although able to “float” in the “z” dimension, the applanation lens 18is secured against lateral motion and is accurately disposed in a stable“x,y” plane with respect to the eye.

As an alternative embodiment, the applanation lens need not be affixedto the apex ring by a “golden pedestal” approach. As illustrated in theexemplary embodiment of FIG. 9, sufficient alignment of the lens 18 tothe plane of the base ring 28 can be accomplished by machining the apexring 30 to include a retaining lip 31 disposed around the bottom edge ofthe apex ring. The applanation lens is inserted into the apex ring fromthe top, and allowed to rest against the retaining lip 31. The lens isnow bonded into position using a suitable glue, such as a UV curingcement. Likewise, the retaining lip 31 might be provided as an annularstructure circumscribing the interior wall of the apex ring. The lens isinserted from the bottom until its anterior surface rests against theinterior lip, at which position it is bonded into place. All that isrequired in any retaining embodiment, is that the lens be positionedwith respect to the lens cone structure such that its alignment in thex, y plane and in the z direction is at least within an approximately+/−30 micron range. In other words, the applanation surface (andtherefore the surface of the eye) must be mathematically definable withregard to a laser delivery system to within about +/−30 microns.

An additional alternative embodiment will be appreciated by those havingskill in the art, when it is considered that the lens might not beaffixed to the lens cone structure prior to the device being assembledon a patient's eye. The applanation lens might be provided as a separatecomponent from the lens cone structure. In this particular embodiment,the applanation lens is constructed as a shallow dish, with sidesextending vertically upwards and having an OD such that it may bepress-fit within the interior of the annular attachment ring. As theattachment ring and applanation lens combination is fixed to the cornealsurface, the applanation lens is able to partially applanate the cornealsurface in order to improve alignment. During the initial affixation andalignment procedure, the attachment ring may or may not be fitted withinits appropriate receptacle in the gripper structure. The attachmentring, either with or without the applanation lens included, might befirst affixed on the patient's eye and the gripper structure loweredover the attachment ring, or, alternatively, the attachment ring, eitherwith or without the applanation lens included, is press fit into itsappropriate receptacle on the gripper structure and the entire compositeplaced over the surface of the patient's eye. In this particularinstance, care must be taken to precisely manufacture the bottom surfaceof the apex ring, since this is the portion of the lens cone which nowcontacts the applanation lens. Contact pressure between the apex ringand the lens now steadies the lens in the desired plane. Needless tosay, the attachment procedures described above hold true for any of thesystem embodiments described above, as well as one in which theapplanation lens is bonded directly to the gripper structure in asuitable position.

After the composite structure is either assembled on the patient's eye,or assembled and then positioned on the patient's eye, the lens cone islowered into position into the central opening of the gripper and thejaws of the gripper are allowed to relax, thereby grasping and retainingthe lens cone in position. As the lens cone is lowered over thestructure, final applanation takes place as the applanation lens iseither further pressurized against the corneal surface by movement ofthe lens cone (if the lens is provided as a separate structure) or asthe lens is moved into contact with the corneal surface, allowing conepressure to applanate (if the lens is provided within the lens cone'sapex ring). In this regard, it is anticipated that ocular pressuredeveloped by the applanation process will not exceed approximately 60mmHg, and will preferably be in the range of about 40 to 50 mm Hg.

The lens cone might be secured to the gripper in a number of ways, inaddition to being gripped by compressive jaws. For example, theattachment ring might have a communication channel provided between thesuction chamber and its interior surface. Accordingly, as the apex ringof the lens cone is lowered into engagement with the attachment ring, asuction is established between the attachment ring and the lens cone'sapex ring thereby securing the lens cone to the attachment ring.Although suction involves a relatively simple application of forcebetween the lens cone and attachment ring, suction (or vacuum) is notthe only attachment methodology which is contemplated by practice of theinvention. Indeed, the upper portion of the attachment ring might beprovided with thin, magnetic material that attracts the lens cone's apexring and provides for secured docking of the lens cone within theattachment ring. Further, the gripper might be provided with a suctionmanifold disposed around the central opening and the apex ring providedwith a flange that overlays manifold openings. As the lens cone islowered into position, and the flange covers the manifold openings,suction is applied thereby securing the lens cone to the gripperstructure. Accordingly, although mating between the lens cone and thegripper/attachment ring has been described in connection with aflexible, press-fitted attachment, a vacuum attachment or a magneticattachment, it should be understood that the only requirement is thatthe lens cone is securely held and maintained in a specific spatialrelationship with respect to the attachment ring and, consequently, withthe corneal surface.

The present invention has been described, above, primarily with regardto aligning of the structure in relation to a human eye in the “z”dimension, while retaining the eye against relative motion along an “x,y” plane. It is also desirable to ensure proper alignment of thestructure with regard to the central access of the eye, i.e., allow thestructure to centrate about the pupil, such that the iris/pupil ispositioned substantially in the center of the central opening of theattachment ring. Turning now to the semi-schematic, top plan viewillustration of FIG. 10, the top surface of the gripper 14 (top beingthe surface opposite that in proximity with the eye) is provided with aset of alignment marks, or fiduciaries, radially disposed about thegripper's central opening 21, on the upper surface of each jaw 26 and 27and surrounding the central opening 21. The fiduciaries are radiallydisposed and, if extended towards the center of the opening, alignedsuch that they will cross at the opening centrum or axis. The alignmentmarks allow a clinician to judge the central placement of an eye inrelation to the opening and eases the clinician's task in accuratelypositioning the attachment ring/gripper structure with respect to theocular centrum, before the lens cone is lowered into position forapplanation. Once the lens cone is in position, the already alignedgripper laterally aligns the lens, in turn, to the eye. If the structureis appropriately aligned such that the eye is substantially centeredwithin the central opening, a nominal relationship will be establishedbetween a laser delivery system and the structural features of an eye inall directions (i.e., x, y, z). This simple mechanical approach obviatesthe need for complex, highly sophisticated eye following and trackingmechanisms.

A number of exemplary embodiments suitable for practice of the presentinvention have been described in connection with various illustrationsof FIGS. 1-10. However, it should be understood by those having skill inthe art that certain modifications, simplifications and expansions maybe made without departing from the spirit and scope of the presentinvention. Specifically, any appropriate laser medium might be used todeliver the incident laser beam without regard to the particular formand shape of the delivery system. In addition, the gripper structureneed not be a unitary structure, for example, but may indeed be hingedin a central portion and the gripper jaws opened and closed in responseto spring tension and compression made between the gripper handles.Likewise, the applanation lens need not be provided with a substantiallyflat applanation surface. Depending on the ophthalmic procedure intendedto be carried out by the laser system, the lens's applanation surfacemay be concave or convex in accordance with an appropriatemathematically derived curvature, without departing from the scope andspirit of the invention.

In this particular regard, it will be understood that some degree ofspherical aberration might be present in an uncompensated laser beam ifthe applanation surface of the applanation lens were curved. However,given the mathematical characterizability of the curvature of theapplanation surface, it should be understood that a laser beam can befocus-compensated in order to accommodate a degree of curvature.

Accordingly, it is to be understood that the foregoing embodiments aremerely illustrative of the invention and that no limitations areintended to either the details of the construction or design other thanas defined in the appended claims.

1. An interface adapted to couple an eye to a surgical laser, theinterface comprising: a lens cone having a base ring disposed oppositean apex ring, wherein the base ring defines a first plane and is adaptedto couple to a delivery tip of the surgical laser such that the firstplane is at a predetermined position relative to the delivery tip; anapplanation lens affixed to the apex ring, the applanation lens having asurface disposed in a second plane such that the second plane isparallel to and at a predetermined position relative to the first plane;a gripper adapted to engage the lens cone; and an attachment ringaffixed to the gripper, the attachment ring being adapted to couple toan anterior surface of the eye such that when the gripper and the lenscone are engaged, the applanation lens is placed into contact with theanterior surface of the eye, thereby placing the anterior surface of theeye in spatial registration with the delivery tip.
 2. The interface ofclaim 1, the applanation lens comprising an applanation surface, whereinthe applanation surface is placed into contact with the anterior surfaceof the eye when the gripper and the lens cone are engaged.
 3. Theinterface of claim 2, wherein the applanation surface defines the secondplane.
 4. The interface of claim 2, wherein the applanation surfacedeforms the anterior surface of the eye when the gripper and the lenscone are engaged.
 5. The interface of claim 1, wherein the attachmentring comprises inner and outer annular flexible walls adapted to engagethe anterior surface of the eye, thereby forming an annular channelbetween the attachment ring and the anterior surface of the eye.
 6. Theinterface of claim 5, the attachment ring further comprising a fluidcommunication channel adapted to couple the annular channel with avacuum source.
 7. The interface of claim 1, wherein the gripper includesa central orifice adapted to engage the apex ring.
 8. The interface ofclaim 7, wherein the gripper comprises a pair of expandable jawsdisposed adjacent the central orifice, the jaws being adapted to engagethe apex ring.
 9. The interface of claim 8, wherein the gripper furthercomprises opposing lever handles coupled to the jaws, the opposing leverhandles being adapted to expand the jaws.
 10. A method of coupling aneye with a surgical laser, the method comprising: coupling a gripper toan anterior surface of the eye, the gripper including an attachment ringadapted to couple to the anterior surface of the eye and to stabilizethe gripper relative to the eye; coupling a lens cone to a delivery tipof the surgical laser, the lens cone having a base ring defining a firstplane, such that the first plane is at a predetermined position relativeto the delivery tip; coupling an apex ring of the lens cone the gripper,wherein an applanation lens is affixed to the apex ring, the applanationlens having a surface disposed in a second plane such that the secondplane is parallel to and at a predetermined position relative to thefirst plane, thereby bringing the applanation lens in contact with theanterior surface of the eye and placing the anterior surface of the eyein spatial registration with the delivery tip.
 11. The method of claim10, wherein coupling the gripper to the anterior surface of the eyeincludes coupling an attachment ring of the gripper to the anteriorsurface of the eye.
 12. The method of claim 11, wherein coupling theattachment ring to the anterior surface of the eye includes: forming anannular channel between inner and outer annular flexible walls of theattachment ring and the anterior surface of the eye; and creating anegative pressure within the annular channel.
 13. The method of claim10, wherein coupling the apex ring to the gripper includes coupling theapex ring with a central orifice of the gripper.
 14. The method of claim13, wherein the gripper includes a pair of expandable jaws and couplingthe apex ring with the central orifice includes engaging the apex ringwith the pair of expandable jaws.
 15. The method of claim 10, whereincoupling the apex ring to the gripper includes placing an applanationsurface of the lens in contact with the anterior surface of the eye. 16.The method of claim 15, wherein placing the applanation surface incontact with the anterior surface of the eye includes deforming theanterior surface of the eye using the applanation surface.